﻿      <p>
        The example demonstrates how a window can be placed inside a wall. The basic format of the wall is 3 meter
        length and 2 meter height with a thickness of 300 mm. The window has a size of 1x1 meter and is placed exactly
        in the middle of the wall.
      </p>
      <p>
        To insert a window or door in a wall it is required to create an opening. The following entities are relevant:
      </p>
      <ul>
        <li>
          <em>IfcWall</em> (or <em>IfcWallStandardCase</em> if geometry representation allows for it);
        </li>
        <li>
          <em>IfcOpeningElement</em>;
        </li>
        <li>
          <em>IfcWindow</em>.
        </li>
      </ul>
      <p>
        The three entity instances have to be connected in 2 different ways
      </p>
      <ul>
        <li>via relative placement;
        </li>
        <li>via topological connection.
        </li>
      </ul>
      <p>
        Each physical object has a placement. The placement is represented by <em>IfcLocalPlacement</em> and can be
        relative to an <em>IfcLocalPlacement</em> of another physical object (in case of aggregation, feature or
        filling relation) or of an spatial structure element. This process of local placements is recursive.
        <em>IfcWall</em>, <em>IfcOpeningElement</em> and <em>IfcWindow</em> each have their own
        <em>IfcLocalPlacement</em>, however the <em>IfcLocalPlacement</em> of <em>IfcWindow</em> is defined relatively
        to the <em>IfcLocalPlacement</em> of <em>IfcOpeningElement</em> and the <em>IfcLocalPlacement</em> of
        <em>IfcOpeningElement</em> is defined relatively to the <em>IfcLocalPlacement</em> of <em>IfcWall</em>.
      </p>
      <p>
        The <em>IfcWall</em> and <em>IfcOpeningElement</em> are connected via the objectified relation
        <em>IfcRelVoidsElement</em>. The <em>IfcRelVoidsElement</em> is connected with the wall via the relationship
        RelatingBuildingElement and to the opening element via the relationship RelatedOpeningElement. Through the
        inverse relationships it is possible to traverse from wall to opening element and vice versa.
      </p>
      <p>
        The <em>IfcOpeningElement</em> and <em>IfcWindow</em> are connected via the objectified relation
        <em>IfcRelFillsElement</em>. The <em>IfcRelFillsElement</em> is connected with the opening element via the
        relationship RelatingOpeningElement and to the window via the relationship RelatedBuildingElement. Through the
        inverse relationships it is possible to traverse from opening element to window and vice versa.
      </p>
      <p>
        &nbsp;
      </p>
      <table summary="wall example">
        <tr>
          <td>
            <img src="../../figures/examples/building_element_configuration_wall-1.png" width="526" height="690" alt=
            "building_element_configuration_wall-1.png 29,1 KB">
          </td>
          <td style=" vertical-align:bottom;">
            <p>
              The Figure 502 shows the parameters used for creating the example data set.
            </p>
          </td>
        </tr>
        <tr>
          <td>
            <p class="figure">Figure 502 &mdash; Parameters of wall, opening and window</p>
          </td>
          <td>
            &nbsp;
          </td>
        </tr>
    </table>
    <table summary="wall example">
        <tr>
          <td>
            <img src="../../figures/examples/building_element_configuration_wall-2.png" width="846" height="594" alt="building_element_configuration_wall-1.png 48,6 KB" />
          </td>
          <td style=" vertical-align:bottom;">
            <p>Figure 503 shows the geometric representation of the example data set.</p>
          </td>
        </tr>
        <tr>
          <td>
            <p class="figure">Figure 503 &mdash; Geometric representation of wall, opening and window</p>
          </td>
          <td>
            &nbsp;
          </td>
        </tr>			
      </table>
